5 Step Seq: A Buchla-Inspired DIY Project by HAGIWO

Hey synth DIYers! Today we’re diving into another brilliant and budget-friendly project from the prolific HAGIWO: the 5 step seq. It’s an Arduino-based sequencer inspired by the unique, groove-making modules from the legendary Buchla Easel.

Project Overview

This module is HAGIWO’s 88th creation, and it’s a special one. If you love the quirky, non-linear patterns from Buchla sequencers (which use odd step counts like 3 and 5), this project is for you. Instead of just copying, HAGIWO has created a modern, digitally-controlled module with a pure analog output.

The brain is an Arduino Nano, but clever design means no DAC or PWM is used for the output. This results in a simple circuit with excellent voltage stability and responsiveness, giving you clean, predictable CV signals.

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Features

This little 10HP module is packed with features:

• Dual-Mode Sequencer: Switch between two distinct operational modes.
  • 1. Step Sequencer Mode (FWD): Classic forward-moving sequencer. You can select 3, 4, or 5 steps to create those famous odd-time-signature grooves.
  • 2. Random Sequencer Mode (RND/TIE):
    • RND: A standard random step generator.
    • TIE: A random mode where steps have a chance of becoming a “Gate” (tied note) instead of just a “Trig.”
    • In random mode, you can select NA (a 256-step full random sequence), 8 steps, or 16 steps.
• Per-Step Control:
  • CV Pots (x5): A dedicated knob for each of the 5 steps to set its CV output level.
  • Trig SW (x5): A switch for each step to turn its trigger output on or off, perfect for creating rhythmic variations.
• I/O and Global Controls:
  • Tempo Pot: Controls the internal clock speed.
  • Level Pot: Adjusts the overall CV output range (0-10V+).
  • Trig In: An external clock input. Plugging in a cable automatically switches from the internal to the external clock.
  • Reset In: A standard reset input to restart the sequence.
  • Trig Out: Outputs a 0-5V Trigger or Gate signal.
  • CV Out: Outputs the main CV signal (0-10V+).
  • LEDs: 5 bright LEDs show you which step is currently active.

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Summary Table

Here are the quick specs for your Eurorack case:

Specification	Value
Format	Eurorack
Size	3U, 10HP
Power	40mA (+12V)
	5mA (-12V)

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Build Cost & Sourcing

One of the best parts of HAGIWO’s projects is the ultra-low cost. This entire module can be built for approximately $11!

Here’s a rough breakdown of the main parts:

• Arduino Nano: $3
• Potentiometers (x7): $2.10 ($0.30 each)
• Switches (x7): $1.40 ($0.20 each)
• Front Panel: $1.50
• TL072 Op-Amp: $0.20
• Other Components: ~$2.80 (resistors, capacitors, jacks, etc.)

For sourcing components, the article recommends checking out HAGIWO’s general list of cheap DIY parts [2]. The circuit uses a common 2SA1015 transistor, but the designer notes that any common NPN transistor should work just fine. It’s also recommended to use high-brightness LEDs so you can easily see your sequence in action.

All the circuit diagrams and Arduino code are available on the project page [1].

Happy building, and see you at the live show!

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Footnotes

[1] HAGIWO’s “5 step seq” Project Page: https://note.com/solder_state/n/nf6c29a7075cd

[2] HAGIWO’s List of Cheap DIY Modular Synth Parts: https://note.com/solder_state/n/n4a62c6d4e56d (Linked from the main article)

[3] Synth Geekery Live Show Link: https://youtube.com/watch?v=tOyRlFShAAE